Antenna system



April'2, 1946. I G. H. BROWN ANTENNA SYSTEM Filed May 30. 1942 2Sheets-Sheet 1 Zsnventor George Brown v j va i wfimw F Fl n 5.; m fl m.0 0 H m 1 bu -mm U 14 m aulrflv 1| 7:. z T a 7 r/ a u i Z m mm ,5 2/1.a m m 7 u n ,i fi/ F; Z d 4 k I (Ittomeg G. H. BROWN ANTENNA SYSTEMFiled May 30. 1942 April 2, 1946.

2 -Sheets-Sheet 2 I DEV/CE I N VEN TOR. fiwrKHBrmr/m BY 1 Arron/5rPatented Apr-2,1946, g

George H. Brown, Haddonfleld, N. J., assignor to Radio Corporation ofAmericas corporation, of i Delaware Application May 36, 1942, Serial No.445,175

4 Claims. (Cl. 25 -11) This invention relates to improvements in antennasystems of the ty'peused to establish overlapping radiation fields, andparticularly to a system with meansfor minimizing the mutual couplingbetween the several antennas of an array and for reversing alternatelythe phase of the currents applied to certain of. the antennas withrespect to the phase of the. currents applied to another group ofantennas, whereby diflerently directed field patterns are obtained insynchronism with said phase reversals.

One-of the objects of this invention is to provide improved means forestablishing two alternately differently directed and overlapping radiofrequency'fields. A further'ob'iect is to provide improved means fordirecting the plane of the axes of said fields atan angle with respectto object is to provide improved means for minimizing mutual couplingefi'ects between the antennas of an array of the type described, and

for energizing all of said antennas from a single I source-in properphase and power relationship to produce the desired field patterns.These and other and incidental objects will become apparent to thoseskilled in the artupon consideration of the following description; withreference to the accompanying drawings, in which Fig. 1 is a' schematicdiagram of a radio frequency distribution circuit illustrating theprinciple of operation of the invention; Fig. 2 is aplan view, partly insection, of an antenna array representing one embodiment of theinvention; Figs. -3 and 4 are elevations, partly in section, of parts ofFig. 1; Fig. 5 is adiagram. of the connections between the antennasshown in Fig. l and a transmitter or other radio device. Referring toFig. 1, a line I, which is shown as a coaxialline, is connected in aclosed loop. The length of line, pr perimeter of the loop, is made oneand one-half wavelengths long at the frequency at which the system is tooperate. Two sources, A and B (not shown), are connected as indicated atpoints.

spaced one-half wavelength apart around the loop in one direction. Thedistance between the two points in theother direction is one wavelength;the difference between the two distances is one-half wavelength.Therefore, any voltage at one of the points of connection will reach theother point bytwo paths and in opposite phases, producing rer'oresultant voltage. Thus there can be no reaction between the. sources Aand B. Two loads, C and D, are likewise connected at suchpoints that-thedifference in the length of transmission the'plane of said antennaarray. Still another lengths of the two paths between them through theline is one-half wavelength, and there can be no reaction between themthrough the network. However, the voltage at each of the loads is aresultant of the voltages at the two sources,

and by providing suitable amplitude and phase relations between the twosource voltages, any desired relation between the two load voltages maybe obtained while maintaining isolation between the individual loadsand, the individual sources. I

Referring to Fig; 2, the array which will be used as an example indescribing the present invention comprises two centrally disposedantenna groups I and 3 and four antennas 5, I, 9 and ii disposed at thesides. Each of the side antennas is a dipole comprising two radiatingsections, each one-quarter wavelength long at the irequency for whichthe system is designed; and

arranged end to end. Each of the groups I and 3 comprises four quarter,wave sections arranged end to end and connected as two dipoles energizedin phase with eac other. The component quarter wave sections may beconstructed of' pieces is of pipe or tubing, centered on rods it runningthrough each group by means of plugs [1, as illustrated in Fig. 3.Metallic tubular supporting members l9 are secured near adjacent ends ofthe members i3, and are also employed as reactance elements, asdescribed hereinafter.

In order to produce the required overlapping radiation fields, thecenter antennas are enerv gized constantly, while the polarities oi theside antennas are alternately reversed. The energy radiated by each sideantenna alternately adds,

to and subtracts from that radiated by the centhe radiated fields, anddirecting theplane of the axis of the overlapping lobes at an angle withrespect to the plane of the array. To give the,

ter antennas, thus producing a resultant field which is deflectedalternately from side to side with respect to a center reference line.Two

central, groups of antennas and two pairs of side antennas are employedin the illustrated arrangement for thepurpose of concentrating desireddifference in direction of the two lobes, each center group is made offour quarter wave sections. 1 The particular arrangement to be used, inany case is a matter of design, determined by the requirements.Ordinarily it is desirable. to

design the system so that the boundaries of the overlapping portion ofthe two ,lobes-are nearly parallel to each other, so that a'smalldeviation in position from-the axis of the overlapping area results ina'large difference in the intensities of the fields produced by the tworadiation lobes at of the total power is radiated by the centerantennas,without switching, and one-fifth is radiated by the side antennas, whichare, switched so that they are periodically reversed in phase.

The currents supplied to the antennas l, 5 and I are in quadrature phasewith those supplied to antennas 3, 9 and II, respectively. The currentssupplied to'the side antenna 5 should be either v exactly in phase orexactly 180 out of phase with that of the center antenna I, depending onwhich lobe is being radiated, if the side antennas 5 and I were arrangedin line with the corresponding center antenna I. Since the side antennasare not in line with the center antennas, their currents must be shiftedin phase with rev spect to the currents in the center antennas.

Referring to Fig. 4, each center group is excited as two hali-wa'veantennasin phase, sectionalized by means of the conductive support-- ingmembers 25 anda shorting member 23. The distance S4 of the member 23from the points where the supports 25 are attached to the antenna isadjusted so that the loop formed by the members 25 and the member 23,together with the capacitance between the adjacent ends 01' the antennaelements, constitutes a high impedance resonant circuit, eflectivelyisolating the two sections. The supports 21 are similarly tuned byshorting members II, and the loop formed by members 2i and 21 is used asa loading reactance across the input terminals of each or the componentdipoles. The e'flfective value of the reactance is determined by thedistance Si between each,

member 2| and the points where the corresponding supports 21 areattached to the antenna. The supports I9 of the side antennas arelikewise employed, in conjunction with shorting members 28, gas loadingreactances or insulators as shown in 8. 2. Referring to Fig. 5, thecenter antennas I and 3 are represented schematically. The componentdipoles 3| and 33 of the antenna I, and the cors,so7,o4o

present at the point 43 will thus result in .edual and opposite currentsat points 45 and 41, since the difference in the line lengths isone-half wavelength. A junction point 5| is also connected to points 45and 41 through quarter wavelength lines. Any voltage at junction 5| willthus produce equal currents in the same direction at the points 45 and41. Since the points 49 and 5| are thus connected together through twopaths difiering in length by one hali wavelength, the voltage at each ofthe two points is cancelled at the other and can produce no effect. Thepoints 49 and 5| therefore may be energized in quadrature phase relationwithout interaction.

If this is done, the resultant currents at points 45 and '41 will be inquadrature with respect to each other and hence the antennas I-and ,3will be energizedv in quadrature, notwithstandingany coupling betweenthem or other antennas. It points and 41 were fed inquadrature directlywithout the above described network, interaction between their radiationfields would be reflectedto th phase shifting networks and makeadjustment of the system difficult, if not impossible; coupling with theside antenna groups would affect the adjustment, and since the sideantennas are periodically reversed, the problem would be furthercomplicated.

The points 49 and 5| are connected through lines of diflerent lengths toa junction point 53. Phasing stubs 5,5 and 51 are connected in theselines one-quarter wavelength distant from the point 53. The stubs 55 and5'! are tuned off the resonance frequency and thus function asreactances connected .across the lines. The line lengths and thepositions and lengths of the phasing stubs are adjusted so that avoltage applied at the point 53 produces voltages at 49 and 5i which areof equal. amplitudes and in quadrature phase. In order to compensate theimpedance mismatch due to the connection of the two antenna lines at 53to the line 6! from the transmltter, a matching stub 58 is connected tothe responding dipoles 35 and 31o! the antenna 3. e

are connected together and to a transmitter or other radio device 35, bylengths of transmission line 4|, which in this case is shown asconcentric line. The component dipoles of the antenna I are excited toradiate in phase; since, as shown in Fig. 3, their respectiveconnections to the inner conductor 43' are reversed, the dipole 33 isled through a line one-half wavelength longer than the line to thedipole 3|, thus producing a 180 phase diflerence between the currentsreaching the two dipoles and causing them to radiate in phase. The totallength of line between antennas 3i and 33 is one wavelength. or anintegral number 0! wavelengths. Since the antennas are connected inreverse polarity to the line, any diflerence in their currents. such .asmight tend to result from coupling with the side antennas, is preventedby transfer of energy from one antenna to the other through the line.The dipoles 35 and 31 are connected like the dipoles 3| and 33. Thejunctions 45 and 41 are connected as follows to be energized inquadrature phase with respect to each other: A junction point 49 isconline M at a suitable point, and adjusted so that no standing wavesappear on the line 5i between the transmitter and the matching stub. Theline 6i may then be made 01' any convenient length.

Each of the side antennas 5 and I is connected through a quarterwavelength line 44 to a junction point 46. The antennas are. connectedin opposite polaritiesrto the line, so they will radiate 180 out ofphase. The side antennas 9 and nected to junction through a threequarter Y wavelength line and to the junction 41 through a one-quarterwavelength line. Any voltage I I are similarly connected to a point 48.The connections between points 46 and 48 and the transmission line 83are exactly like those shown in Fig. 5 between points 45 and 41 and theline 6|. To provide periodic reversal oi the polarities of the sideantennas 5, I, 3 and II, the phase of the voltage fed into the line 63is reversed. This is done by connecting the line 53 to the transmitteralternately through two paths, one of which is one-half wavelengthlonger than the other.

Thelines 81 and 58, forming the two paths. are connected to the line 53at the point 65, and to a line II at point I3. If the line 69 isshort-circuited at. a point 15, it will present a very high impedance atthe points 85 and 13 which are each one-quarter wavelength distant fromthe short circuit, and no energy will flow into it at either end,Similarly. if the line is short circuited at a point vH, an odd numberoi quarter wavelengths distant from both points 35 and 13.

it will present substantially an open circuit at those points. Thus, itthe lines are shortcircuited alternately at points 15 and I'I by meansscheaeeaecs inatically indicated at 19, the voltage at the point 85 willbe alternately in phase and out 01' phase 7 with respect to the voltageat the point 13, and

' polarities oi the antennas s, 1, a and will be reversedcorrespondingly. The switchingmeam 19 may be of the type described in U.8. Patent No. 2,189,549 to William D. Hershberger. Power divisionbetween the center antennas and the side at a common point, and/phasingcircuits 'includ-" antennas is accomplished by providing two quarferwavelength sections 81 and 83 in parallel with each other :and inserieswith the line II. This causes the impedance atthe point 81 to bereflected at the point 89 as an impedance oneiourth as great.

A quarter wavelength section. is provided to the lengths o! the twopaths through the network from one of said latter points oi connection.to the other diiier by anodd number of hall, wavelengths, whereby thevoltage at each oi said points is unaflected by that at the other, athirdtransmission line connected to bothof said supply-linesingreactanee elements shunting said supply lines,

at critical points whereby the volta e at the point of one of saidsupply linesto said parallel con- I nected lines is maintained inpredetermined phase act as impedance inverter, so the impedancepresented at the point'9l by the side antenna circuit.

' is four times as highas it is at the point 81, and four times thatpresented by the center antenna circuit through the line 8!. Thusone-fifth oi the power supplied from thedevice 39 through the line willflow to the side antennas, andv iourfifths of the power will 'fiow-tothe .center antennash The length of the line 6| may be trimmed to securethe required phase relations between the center and side antennas. Animpedance matching stub Sils connected to the line 03' to compensate themismatch caused by connecting the lines 85 and 6| together to the line93.

Thus the invention has been described as an antenna system arranged toproduce alternately tion'may be used in other applications where it isdesirable to avoid mutual coupling between radio devices and yet connecta plurality oi such and amplitude relation to that at theIpoint ofconnection or the other 01 said supply lines to the other of saidparallel connected lines, impedance converting means connected betweensaid source of radio frequency energy and all oi said'side antennascomprising two quarter wavelength line sections connected in parallelwith each other and in series with a third quarter wavelength linesection, whereby said side antenna circuit and said center antennacircuit present diil'erent impedances to said source'and takecorrespondingly different proportions oi power. therefrom.

2. An antenna system, 'comprlsing two groups oi antennas, each of saidgroups comprising a centrally positioned antenna and two antennasarranged at the sides-oi said first antenna, means for energizing eachof the antennas or one of said groups in predetermined ,phase withrespect to the corresponding antennas of the other of said groups,comprising,ior each pair of correspond-5 (sing antennas, a on lineconnected in a closed loop, with said pair of antennas connected to saidloop at points such that the difference in lengths or the two pathsaround said loop between said points is one-halt wavelength, two lead-inline's connected to said loop at points such that devices to a commoncircuit. For example, a radio transmitter and a radio receiver may be;

connected 'tola common antenna system by a network according to theinvention, and arranged so that no energy is transferred from one to theother through the circuit.

.. I claim as my invention:

-1. A system for producing overlapping radia- I tion fields includingtwo groups of antennas, each oi said groups comprising a centrallypositioned energy so as to be energized constantly, and two sideantennas arranged at the'sides of said first antenna, switching means,and connections from said source through said switching means to saidside. antennas so as to periodically reverse said side antennas inphase, means for energizing the antennas of one of said groupsinpredetermined,

phase with respect to the corresponding antennas of the otheroilsaidgroups comprising two transmission lines, each an integral numberof half antenna. connected to a source oi'radio frequency wavelengthslong at the irequencyat which the Y I system is to operate, extending inparallel con-- nection-between correspondingpoints in the circuits orsaid antenna groups, said lines differing in length by an odd number 0!half wave-lengths,

7 tionship. Y 4. 'iheinventionassetiorthinclaimswherein the difierencein lengths of the two paths around said loop between said latter pointsis one-hall wavelength, phasing means including reactanceelementsshunting eachoi said lead-in lines, two 1 supply linesgeach connected toone pair of said lead-in lines at a commonpoint, switching meansarranged in oneoi said supp y" lines to vary the eilective length orsaidiine, a radio device con,- nected to both 01' said supply lines at acommon point, and impedance inverting means in one of said supplylinesarrangedto present at said radio A device an impedance of diflerentmagnitude from that presented by the other r said supply lines.

3. A directiv'eiantenna vsystem including two groups or radiatorelements whichare to be en-" ergized'in a predetermined phaserelationship to each other, an electrical network having two pairs 1 ofconjugate terminals, connections from said groups respectively to oneconju te pair of said network terminals, 0. common supply line for saidelements and branch-lines connected from said common line to the otherconjugate pair oi said network terminals, said branch lines diilering'i'romeachotherinlength byan amount related in a predetermined manner tosaid phase relsv said network includes a transmission line 1% wherebythe voltage at each 0! said corresponding points is ,imafiected by thatat the other 02- said' points, two supply lines, each connected to oneor long connectedin a closed loop and" .said coniutateterminals comprisepoints la svelens 'saertonaidune.

' amass n.

l 3* said parallel connected lines at such a point that

